"The news from Bucharest is that the regime is crumbling/ the way the rocks on the shore erode – by seeming not to." The lines are from Patrick McGuinness's 2010 collection, Jilted City, in what claimed to be a translation from the work of Liviu Campanu, a Romanian poet. In fact they were by McGuinness, who edited Campanu into the history of the Ceausescu regime, reversing the absurd process by which its real dissident authors were edited out. The invented voice gave McGuinness licence to reflect on the end of Romania's communist era but it also enriched the book's meditation on other endings, looking back to earlier poems about the loss of a mother tongue and the death of parents. The brave face, the sudden collapse. This is how people, like governments, fall apart.

Unlike Campanu, McGuinness was there. The Last Hundred Days – his Booker-longlisted first novel – again draws on his time in late 1980s Bucharest. Offered a job in a Romanian university, the unnamed narrator becomes enmeshed in the complicities of the doomed dictatorship. He falls in love with the daughter of a party apparatchik and falls in with a dissident group of people-smugglers. He gains two mentors: the seedy academic Leo (who moonlights as a pillar of the booming black market) and the elderly, debonair Sergiu Trofim, a sidelined luminary of the pre-Ceausescu days who is writing a secret memoir of party corruption.

While Trofim writes two manuscripts – one for the censor and one to be smuggled abroad – Leo scribbles his own book about Bucharest, "The City of Lost Walks", a travel guide to a storied city disappearing under triumphalist party architecture. Like a situationist Harry Lime, he spends his days psycho-geogging the crumbling city and his nights on a more dangerous dérive through the "occult… subterranean branch lines" of suppressed commerce.

McGuinness is similarly interested in incongruous maps, in comparisons where something striking emerges from the imperfect fit between misaligned cartographies. The last days of totalitarian Bucharest overlay the memory of a tyrannical father, crippled and dying of cancer. The "small proprieties" in which the Ceausescus absurdly indulge during their trial – "the way she buttons up her coat… the way he strokes her hand" – are made poignant by the fading recollection of a dead mother. At the same time, the unrest of 80s England bleeds into the margins: tanks in Piata Republica or the Wapping riots? Elena Ceausescu's handbag, or Margaret Thatcher's? This is not the sort of novel to force such alignments into congruence but they link The Last Hundred Days to a wider European experience outside the communist enclave of Bucharest.

Memories of the poetry nag at the novel. A museum where the curators save power by switching on only the lights of the room being toured is in one poem in Jilted City "a metaphor for History"; here it is "like a tide of darkness".

That reworking is more than an alteration: it improves the image by loosening the grip of the writer, registering the implication without policing its significance. Admirable in itself, such self-control sometimes feels like constraint, as when characters' political conversations drift into seminar-ese ("But you are under the misprision that the liberal capitalist state works…"). McGuinness's talent is clearest in the play of local effects: the boredom that drags at the inhabitants of a police state "like shingle scraping at a boat's hull", or the youth group that passes by like "a phalanx of communist Tintins".

"I am a camera," declared another poet in an autobiographical novel about a country in crisis. From the cabarets and the lodging houses, Christopher Isherwood recorded Germany's slouch towards nazism, and Isherwood's Berlin novels come to mind in reading The Last Hundred Days. But McGuinness knows that cameras lie and photographs can be doctored. With his view from the university and the nightclubs, he offers something more complicit and more sceptical about its own objectivity, a glimpse of the moment when Romania's cold war began to thaw.